Step-and-repeat X-ray/Photo hybrid lithography for 0.3-µm MOS devices

X-ray / photo hybrid lithography is proposed as a method for achieving high resolution and high throughput in sub-half-micrometer VLSI fabrication. Distortions and correction techniques are discussed for accurate registration between X-ray and photo levels. Inherent distortions caused by each type of lithography are measured in advance. These distortions are corrected by introducing a linear shrinkage factor into e-beam data preparation for X-ray mask writing. The overlay accuracy between X-ray and photo levels and also between two X-ray levels is less than 0.15 µm (σ). A three-layer resist system is introduced to fully utilize high-sensitivity and high-resolution features of an X-ray positive resist, FBM-G. An application of hybrid lithography to 0.3-µm MOS devices is presented. The results indicate that further application of X-ray / photo hybrid lithography to the sub-half-micrometer device fabrication process is feasible.